1. Technical Field
This invention relates to polarized lens of multifocal.
2. Description of the Related Art
Polarizing lenses have their effect to prevent reflected light from going into the eye, and in particular they prevent reflected light from water surface, snow surface, and road surface, and their need is increasing in sports and other daily living. Further, since the demand for these polarizing lenses is expanding in senior generation, the demand for multifocal polarizing lenses is increasing. With regard to the multifocal plastic lens, there has not so far been a low-cost lens that has both durability and impact resistance.
Further, an addition power segment for multifocus has been manufactured of resin different from that of a bench lens, or has been arranged on the surface of a lens in many cases. When the addition power segment is arranged on the front surface side, it shows up, and the polarizing member must be arranged along the shape of the addition power segment, and air gets in between film and mold during molding and the degree of the addition power segment becomes uneven, and other failure occur in its manufacture, which has been a problem in the prior art.
Furthermore, conventionally the addition power segment has been manufactured separately from the bench lens and attached to the bench lens in many cases, however, the addition power segment is as extremely thin as around 0.2 mm, and it may cut the hand of a worker in attachment work, which has been another problem in the prior art.
With regard to the point that the existence of the addition power segment is seen from the outside in the state where eyeglasses to which multifocal lenses having this addition power segment in its inside is worn, by making the transmittance of the polarizing film at a specified range, the existence of the addition power segment becomes not perceptible from the outside, which has been found by experiments by the present inventors.
Moreover, in the multitiered constituent of the polarizing member, resin expanding to both the polarizing film and sandwich resin, however, studies have not been made on the adhesion compatibility between the stretched resin and the polarizing film, further the combination and expansion of resin of constituent member as the bench lens heretofore. And, the constituent resin of this polarizing member, or the bench lens molded resin and the molded resin of the addition power segment are generally formed as separate resin, in order to have different refraction index, and accordingly, detachment and durability problem, expensive lens cost may be caused, which has been still another problem in the prior art.
Further, the polarizing film itself is extremely expensive. Accordingly, it is most preferable to realize the original polarizing effect with a small use amount of this polarizing film. Further, this polarizing member is made of poly vinyl alcohol and the like, and the resin is stretched so as to have polarizing function, and poly carbonate to sandwich both the surfaces thereof are also stretched in order to reduce deformation. When the bench lens is formed further on this polarizing member, the polarizing film is heated over Tg point (glass transition point) by molten injection resin. Since the thickness of molded lens is thin, by stress of the polarizing member expansion ties to return, curve of axial direction/counter axial direction of lens after molding becomes different, which has been found, and by efforts by the present inventors, it has been found that this deformation can be reduced by partially cutting the polarizing film.